What condition describes aggregates that have absorbed all moisture but show no visible film of free water?

The condition described fits the definition of "saturated surface dry (SSD)" aggregates. In SSD condition, the aggregates have absorbed moisture to the extent that all their internal voids are filled with water, yet they do not display any visible free water on their surfaces. This state is crucial for concrete mix design, as it ensures accurate water-cement ratios when aggregates are incorporated into a mix.

Achieving this condition helps to maintain the integrity of the concrete by preventing excess water from being added, which can lead to dilution of the cement paste and ultimately affect the strength and durability of the concrete. It is particularly important in situations where precise water content is necessary for achieving the desired performance characteristics in the final concrete product.

In contrast, completely dry aggregates would have no moisture content at all, oversaturated aggregates would have free water present on the surface, and partially saturated aggregates would have some moisture present but not enough to be considered SSD. Each of these conditions impacts the behavior of the aggregate and the quality of the concrete mix in different ways.